Principal Investigator / Author(s): Goldstein, Allen

Contractor: UC Berkeley

Contract Number: 09-316

The primary objective of this project was to investigate 1) the contributions of various emission source categories to organic aerosol (OA) and 2) the formation pathways of secondary organic aerosol (SOA). The goal was to provide insights into effective air pollution control strategies. Hourly measurements were made during the CalNex 2010 Field Study and positive matrix factorization (PMF) was performed on particle-phase organic species in PM2.5 to identify major sources of OA and to examine SOA formation pathways. The formation of SOA was through multiple pathways, with the largest fraction of SOA formed through condensation of gas-phase oxidation products onto particles. Effective control measures to reduce OA in Bakersfield should focus on reducing sources of organic precursors during the day, especially regional sources. Controlling the chemical species actively involved in the formation of SOA, such as ammonia, should also reduce the concentration of SOA. However, it should be noted that reducing ammonia emissions could also form more nighttime SOA. Additional research is needed to examine the net effect of ammonia controls for reducing OA concentrations.